Japanese government officials searched the headquarters of Subaru Corporation on Wednesday after the automaker admitted it had falsified mileage and emissions data on new vehicles at one of its domestic plants.

At the end of last month Subaru reported to Japanese authorities it had systematically falsified fuel economy and emissions data in the final inspection process at its Ota plant in Gunma Prefecture Gunma for at least six years, until as recently as the end of last year.

The company also said that due to a lack of earlier records, the fraud may have taken place for much longer - possibly even since as far back as 2002. 

Investigators from Japan's Ministry of Land, Infrastructure, Transport and Tourism also plan to question senior officials at the automaker as part of probe before deciding what penalties to impose.

According to local reports, the company said the data was falsified on the orders of the head of the plant's vehicle inspection department but managerial staff were unaware of what was taking place.

Subaru came under fire late last year after the company admitted that final inspections on its cars had been carried out by unqualified staff, triggering a massive domestic recall.

In a public statement, Subaru's management acknowledged it needed to reform its corporate culture and that "management and employees will work collectively to restore lost trust".